New evidence has surfaced that Army Staff Sergeant Robert Bales may have been on mefloquine during his March, 2012, rampage that killed 16 Afghan civilians.

I first wondered if Bales had been on the anti-malarial agent, also known by its trade name, Lariam, on March 20, 2012, a week after the massacre. I noted that “this medication has been increasingly associated with neuropsychiatric side effects, including depression, psychosis, and suicidal ideation.” A number of other media outlets picked up the story.

But that was just a working hypothesis, absent evidence on Bales’ use of the drug. Strangely, the government never confirmed — or denied — that he had been given Lariam.

My colleague and co-author of a paper on the subject of mefloquine and forensic psychiatry, Dr. Remington Nevin, recently obtained a so-called “adverse event report.” That’s a document describing a negative side-effect to a medication. This particular document details a “medically confirmed” event of homicide by a Soldier taking mefloquine.

Nevin got the report from Action Lariam for Irish Soldiers (reach them at mefloquineireland@gmail.com), for the Irish network RTÉ. The broadcaster prepared a report on the possible links between Lariam and suicides among Irish peace-keeping soldiers.

We have been unable to determine who wrote the initial report, but generally they’re turned in by physicians or others involved in the case. The document suggests that on March 29, 2012, Roche, Lariam’s maker, received a report that someone involved in the homicide of 17 civilians had been taking mefloquine.

On April 11, Roche forwarded the document on to the FDA, as it is required to do.

Here is the key passage from the much longer document, which has the relevant parts highlighted:

Homicide [REDACTED] A patient of unknown demographics started on mefloquine (therapy details unspecified) for an unknown indication. After an unspecified duration, the patient who was a soldier experienced homicidal behaviour which led to homicidal killing of 17 [REDACTED]. It was reported that the patient was suffering from traumatic brain injury (TBI) and was administered mefloquine against military rule (mefloquine is directly contraindicated in patients with TBI as per [REDACTED] rule).

The report is a summary — not the original report — so important details, beyond those redacted, may be missing. It also does not name Bales. But it’s unlikely there was another Soldier with a traumatic brain injury in this time frame connected to 17 homicides (that was the original number; further investigation concluded 16 people had died).

The absence of basic demographic information and other medical information is also noteworthy. It suggests that the person doing the reporting is less well-informed on such an apparently significant case than they should be. But many adverse event reports are incomplete. While this report could represent a spontaneous report from someone without first-hand knowledge of Bales’ case, it is reported by Roche as “medically confirmed” — suggesting an authoritative source. It is also possible that this was an initial report, that was later found not to be true.

Bales’ attorney, John Henry Browne, did not return calls seeking comment on the document. On June 5, the 39-year-old married father of two pled guilty, removing the possibility that he will be executed for the crimes. The plea also avoided a full-fledged trial in connection with the case, which remains murky. Bales, who was on his fourth deployment in 10 years, is slated to be sentenced in August to life imprisonment, possibly with a chance for parole.

A year ago, Nevin testified before Congress on mefloquine’s toxic effects that may mimic PTSD and TBI, as well as contributing to suicide and violence. The Senate Appropriations Committee’s subcommittee on defense considered markup language proposed by Senator Dianne Feinstein, D-Calif., to basically bar Lariam’s use by the U.S. military, and to sponsor additional research into its neurotoxicity. But the provision didn’t make it into law.

Earlier this year, the Defense Department quietly reinforced its standing policy making mefloquine the drug of last resort. However it remains available in the military’s pharmacies to be mis-prescribed to soldiers with TBI and other mental-health conditions, with potentially devastating consequences.

This new report should compel the Pentagon to clear the air on whether Bales was on mefloquine when he killed 16 Afghans, and – if so – to what degree mefloquine may have been the real trigger.